FREE-LIVING FRESH-WATER NEMATODES 51 



far behind the base of the pharynx as this latter is behind the anterior 

 extremity, are one third as wide as the corresponding part of the head, 

 and consist of obscure spirals of one wind. There are no eye-spots. 

 The oesophagus begins as a tube about half as wide as the correspond- 

 ing portion of the head, but expands very slightly as it passes back- 

 ward, so that at the middle it is about two-thirds as wide as the 

 middle of the neck. Behind this point it diminishes. There is a 

 break in the musculature somewhat similar to that occurring in Cephalobus. 

 At the break, which occurs at the beginning of the fourth fifth, the 

 oesophagus is somewhat narrow, about half as wide as the corre- 

 sponding portion of the neck. It finally expands to form the ellipsoidal 

 cardiac bulb, which has a relatively large, chitinous, striated, complicated, 

 three-fold valvular apparatus half as wide as itself. There is a truncate- 

 conoid cardia about one-third as wide as the base of the neck. The lining 

 of the oesophagus is a fairly distinct feature. The thick-walled intestine, 

 which is separated from the oesophagus by a constriction, soon becomes two- 

 thirds as wide as the body. It is composed of cells of such a size that four 

 are required to build a circumference. The walls of these cells are refrac- 

 tive, so that the cells are readily distinguished from each other, though there 

 is no distinct tessellation. These cells contain minute very uniform granules. 

 The lining of the intestine is refractive, so that the lumen is distinctly to be 

 seen. From the rather inconspicuous anus the rectum, which is about as 

 long as the anal body diameter, extends inward and forward. The internal 

 sexual organs are double and symmetrically reflexed. The tail is conoid 

 from the anus to the subacute terminus. This species is related to those 

 described by Dr. de Man under the name of Teratocephalus. It is doubtful 

 whether these forms will not have to be subdivided at some future time, 

 after the accumulation of the necessary data. 



Habitat: Maple River, Michigan. Sublimate to balsam. 



ALAIMUS, de Man, 1880. 

 Fig. 9, Plate IV. 



.2 ii. 19- 35- 92. 

 9. Alaimus simplex, n.sp. 



.3 .8 .9 i.i -6 

 The thin, transparent layers of the colorless, naked cuticle would ordi- 

 narily be described as destitute of striations. Very minute striations may 

 be observed in the subcuticle at the extremities, when the specimens are ex- 

 amined under favorable conditions with the highest powers. There are 

 obscure traces of lateral wings. The conoid neck ends in a rounded head 

 not set off in any way. There are no distinct lips, and only the faintest 

 possible indications of labial papillae. These are so obscure that it has been 

 found impossible to enumerate them. There is no pharynx and the mouth 

 opening is exceedingly minute. No amphids or eye-spots have been seen. 



